MAGNETIC PERMEABILITY OF NICKEL AND COBALT 



65 



of the outside layer and also of the pieces of paper which were used to 

 separate the layers of wire; hence the ring at high magnetizing-powers 

 must have been at a somewhat higher temperature than the bath, to an 

 amount which it is impossible to estimate. It is probable that it was 

 not very great, however; for at this high temperature continued for 

 hours it requires but little increase of heat to finally destroy the silk. 

 We can, however, tell the direction of the error. 



We see, on comparing Tables I and II with Table III, the great 

 effect of heat on the magnetic properties of nickel. We see that for 

 low magnetization the permeability is greatly increased, which is just 

 opposite to what we might expect; but on plotting the curve we also 

 notice the equally remarkable fact, that the maximum of magnetization 



ZO.OOO 40.000 



eo.ooo 



1. Curve at 15 C. 



2. Curve at 220 C. 



is decreased from 33= 63,400 or 3 = 4940 to 33= 49,000 or $ = 3800. 

 This curious result is shown in the annexed figure, where we see that 

 for low magnetizing-f orces p is increased to about three or four times 

 its value at 15 C., and the maximum value of // is increased from 222 

 to 315. When 33 has a value of 32,000, p is not affected by this change 

 of temperature, seeing that the two curves coincide; but above that 

 point fji is less at 220 C. than at 15 C. In other words, if nickel is 

 heated from 15 C. to 220 C., the magnetization of nickel will increase if 

 the magnetizing-f orce is small, but will decrease if it is large. It is impos- 

 sible to say at present whether increase of temperature above 220 will 

 always produce effects in the same direction as below it or not. 



These remarkable effects of heat, it seems to me, will, when followed 



out, lead to the discovery of most important connections between heat 



and magnetism, and will finally result in giving us much more light 



upon the nature of heat and magnetism, and that equally important 



5 



